Add BF16 support check for MUSA backend

src/transformers/utils/import_utils.py

@@ -638,6 +638,8 @@ def is_torch_bf16_gpu_available() -> bool:
     if is_torch_mps_available():
         # Note: Emulated in software by Metal using fp32 for hardware without native support (like M1/M2)
         return torch.backends.mps.is_macos_or_newer(14, 0)
+    if is_torch_musa_available():
+        return torch.musa.is_bf16_supported()
     return False